The present invention relates to an apparatus for changing the rolls of a vertical rolling mill stand.
In general, an installation for continuous casting of slabs has low productivity due to its low casting speed. In order to improve productivity, a slab with an extremely large cross section (of the thickness of 280 to 300 mm and of the width of 1800 to 2000 mm) must be cast. However, the slab with such a large cross section must be decreased in cross section before it enters a hot strip mill (which produces coils of strip with the width ranging in general from 800 to 1500 mm). In order to attain such high reduction ratios, a sizing mill consisting of vertical and horizontal rolling mill stands is employed.
The present invention is directed to an apparatus for changing the rolls of the vertical rolling mill stands in the sizing mill or of other vertical rolling mill stands.
The vertical rolling mill stands use in general caliber rolls. Because of their constructions and their difference in peripheral speeds, they wear very rapidly so that they must be replaced with new rolls almost every few days.
When the continuous casting of slabs is interrupted whenever the caliber rolls are changed, it is impossible to improve productivity. It follows therefore that the roll replacements must be made without interrupting the continuous casting operations.
The conventional apparatus for changing the rolls are such that each roll is replaced by a crane with a C-shaped hook or the like at the line center so that the rolls cannot be replaced when a slab is passing the rolling mill stand. As a result, the slab which is continuously cast must bypass the vertical rolling mill stand when the rolls are being replaced in order to prevent the decrease in productivity. To this end, an additional bypass line must be provided, which is the waste of money.
The primary object of the present invention is therefore to provide an apparatus which may permit the replacement of the rolls of a vertical rolling mill stand even when a slab is passing therethrough.
Another object of the present invention is to eliminate both the space on the ground for storing new rolls and the additional line bypassing the rolling mill stand.
A further object of the present invention is to provide an apparatus which may be remote controlled in changing the rolls of a vertical rolling mill stand.
The present invention will become more apparent from the following description of the preferred embodiments thereof taken in conjuction with the accompanying drawings.